Why does the texture of my hair weave get worse after washing it? ?

I wear sew ins religiously. I've been noticing lately that every time I wash my weave (which isn't too often)the textures of my weave changes. And its not changing for the better. :( I thought it cld have been the hair I was buying so I upgraded. Then I thought it cld be the products so I changed one. Still the same results occur. :( I have remy hair in right now and I am afraid to wash it but I need to. I accidentally put a little too much wild growth on my scalp in between my braids and it got on to my hair a little. By the way I use baby shampoo to wash my weave and any kind of decent conditioner. Should I be using a leave in conditioner? Does anyone know y the texture changes? Also id like to know...after washin a weave(only the hair,not your scalp) should you blow dry the hair or let it air dry? Which is better and why? please answer and any tips are welcomed. Thank you in advanced