Q.what do underfed geraniums look like?
I genwerally feed my geraniums every 1 to 2 weeks with miracle grow liqid fertilizer. We had a huge rain per iod of days. the plants now look cupped and light green and with dark lines of the spines showing thru.

Certified GKH Gardening Expert
Is this a specific flowering fertilizer? High nitrogen fertilizers will tend to halt flower growth, but yield large dark foliage. It is best to apply something a little higher in phosphorus and potassium and lower in nitrogen for plants that flower profusely like these do.
Some infections can steal nutrients as well, and geraniums can be susceptible to infections during wet seasons. It is best to make sure that the container has plenty of drainage holes to allow water out of the container.
If you can include a photo, I can see what the problem might be. It would help me to make a better diagnosis.