I purchased zucchini, pepper, and tomato plants recently from a retail outlet. I brought it home and transplanted them to my raised bed. It has been two weeks and the plants don't seem to be growing many leaves. Some of them have flowers but leaves are small or not growing as fast I would have expected. Did I plant them too late (mid June)? Do I need to add special fertilizer to see leaf growth (I already put vegetable fertilizer but not sure what ratios I need to use to get green growth. I am in northern california. If I missed the growing season, what other vegetables should I plant now?
If you purchased the plants from a box store or from a nursery that does not raise its own stock, then it's possible your plants had too much growth inhibitor applied to them. This link shows a commercial product that is used to treat plants for better shipping. If I'm right, it's possible that the plants will eventually metabolize (if that's the word I want...) the product and begin growing again, but I do know of cases where this did not happen for nearly an entire growing season.
Note that plants treated with most inhibitors show very compact growth, with short internodes.
EDIT: Here is additional information on inhibitor use on vegetables.
Maybe just patient with them, as it takes a couple weeks for transplants to stabilise; the way they were planted matters too. If the roots were sort of loosened, then they should be ok, as long as some good soil is well around them, and they're watered in etc. The tomatoes(likely) & peppers flowering is a good sign, just keep them adequately and evenly watered, without ever really drying out. The soil matters a lot, but should be ok if you've had good results previously.
Wouldnt add much nutrient until they have been growing a bit. The squash grow sort of slow at first, the peppers always grow slow, and the tomatoes may grow more rapidly, depending on variety. Might want to glance if the tomatoes are a small variety, and some peppers are quite little also. Bell peppers are usually the bigger ones, and some of the larger long ones.
There may be instructions on the nutrient container, but generally the plants should be established before applying any nutrient.
There should be enough time to get some fruits!
If they remain fairly small/ are very small varieties, might be able to bring them in when it becomes cold, and they might do ok all winter, next to a window!
Small type round radishes, & green onions grow rapidly and do very well, and some smaller varieties of carrots do well also! Possibly plant them a bit separated rather than thinning them: With good germination rates, simply planting them a bit spaced, rather than closely planting & then thinning, may be efficient. And the plants that remain after thinning get disrupted. They generally need adequate daily watering.