Its normal for some flowers to drop. If its been going on for a really long time and no peppers are being produced, then there could be a couple of issues.
1. Light: From your pictures, I'm assuming that your peppers are outside, so light shouldn't be an issue. If they are inside, you really need to make sure your lighting is sufficient.
2. Outside temperature: The outside temperature needs to be warm enough for the plant to produce the peppers.
3. Water reservoir temperature: If your water temps are too hot then that can stress the plant, lead to root rot, and block flowering.
4. Nutrients: You said you switched to bloom nutrients, which is exactly what you want. What brand of nutes are you using? You need to make sure that (a) You have enough nutrients, and (b) that your nutrients aren't too concentrated, so check the PPM levels to make sure they aren't too high.
5. Pollination: If your peppers are outside, the bees should pollinate them. If they are inside or you think that the bees aren't pollinating them, try to hand pollinate them. You can do this by taking an electric toothbrush and gently shaking the flower with it. You can also try and get a q-tip to apply to the anthers and then to the stigma of the plant.
Judging by your situation, I would say that you most likely have a pollination problem, or maybe a nutrient problem in terms of PPM.