Cat problem its urgent and important

i have two male persian siamese cross (male). I dont give them canned
food. Only boiled potatoes and boiled fish, mashed together. My street
cats eat this too. But i am having a problem nowaday. both of them are
1 year old. One of them has started crying. He cries alot, and ****es
little drops any where in the house, though he is potty trained. he
never did this before. I took him to the Gov. Vet hospital. The doctor
gave him 2 injections and B-Complex syrup to be given 3 times a day,
but no change. What should i do.
one thing more the penis spot my my cat stays dark red. I dont know
why/?