Help with container Zucchini/Butterbush

I am growing squash for the first time, some is planted in a raised bed and some in containers. The first set of true leaves on a few of my plants started to turn slightly yellow and get some brown spots. The plants still seem to be growing new healthy leaves. They are planted in Kellogg's Raised Bed and Container Potting Mix. I have attached a couple of pictures. The larger plant is a dark star zucchini, this one looks the worst. The smaller plant is a Butterbush winter squash, and it is just starting to yellow and get some brown spots. Both are planted in 16" plastic pots with drainage at the bottom, and are watered every day or two when the top inch or two of soil dries out. Any help would be much appreciated.

This message was edited Apr 20, 2015 7:33 PM

Looks like some very poor potting soil. Is there as much wood chips as it looks like.
Wood will draw all the nitrogen out of the soil to decompose.
I would get some Miracle Grow potting soil, (or some other good grade), & replant the pots.
Also don't water to much or you will drown the roots.
Good luck.

INGREDIENTS: Recycled forest products, coir, perlite, dehydrated chicken manure, composted chicken manure, hydrolyzed feather meal, peat moss, kelp meal, worm castings, bat guano

This product does contain fertilizer (slow release, mostly).
Older leaves turning yellow are often a sign of nitrogen deficiency, or of over watering.
If the new growth grows fast, and the leaves get large pretty fast, then it is not nitrogen deficiency.
If the new leaves go pale, and do not really get going, then it is nitrogen deficiency.

Could be other nutrients, too.
I wonder about the pH of such a blend, too. Looks too acidic.

This message was edited Apr 21, 2015 5:25 AM

Lots of stuff I wouldn't want in a soil mix.
Many, many years ago, I was offered wood chippings from a tree service. I mulched my flower beds with that stuff. Plants looked just like these squash. I was told the wood was robbing all the N.
Removed all the wood mulch & the plants started looking better. Now I use cypress mulch which doesn't break down.
That's the reason I suspect the forest products.

Thanks for the replies. There are a lot of wood chips in the soil. I forgot to mention that I also added about 3 tablespoons of slow release fertilizer granules (4-6-3 analysis) to the soil when planting, not sure if this would help. I think I will try to adjust the watering first, any suggestions on how to tell when it is time to water? I am a little concerned about re-potting because of everything I read about squash being fairly delicate when it comes to transplanting. But at the same time I would like the plants to be healthy so we have something to pick in a month or two. Thanks again for the help.

Easiest way is to stick your finger into the soil right next to the old root mass of the plant. Where the old roots meet the new soil should be well watered when you apply the water, then it should start getting dry before you need to water again.
As the plants get older you will check farther away from the original roots, and deeper.
A freshly sharpened pencil will work, too. Stick it in to the depth you want to check and see how dark it becomes. Darker = wetter, so wait longer between watering. Light or blotchy = drying out, good to water.

Here is a picture of my other squash plants that are in a raised bed. This soil is a 50/50 mix of the Kellogg soil described above and last years soil/compost mix. Tomatoes/peppers were grown in last year's soil. The two on top are dark star zucchini, and the two on the bottom are yellow crookneck. One plant is doing very well, with large dark green leaves. The others are struggling much like the ones in containers. Should the dark star leaves be getting this large and dark green as well? They seem to be getting to be about 2 inches before starting to yellow. Would a foliar spray of fish emulsion help me to determine if there is a nitrogen deficiency?

Foliar spray is a good idea! Make sure you get the under side of the leaves.