Charlotte and Crystal must be very special people to you, and it sounds like the three of you are very good friends. I'm sure they value your friendship as much as you value theirs. Have you tried telling them that you think they have very beautiful eyes? Compliments like these will surely melt anyone's heart. You might even get some feedback on how they feel about you this way. You never know that they might have the same feelings about you, and that they are just hesitant in telling you.
I know it's very hard to tell friends something that you think might ruin your friendship with them. I have experienced this in the past as well, but you don't have to say anything if you don't want to. However, you can always talk to others that you trust like your mom or other close friends that you trust. Having someone that is willing to be with you and simply listen to what you have to say can be very helpful and comforting. You could also let your friends know that you think they're very special people, compliment them on their beautiful eyes, and that you value their friendship very much. I say these things to my best friends all the time, and they say the same things back to me. Friendships and relationships are often built on mutual feelings toward each other. Your true friends value your friendship as much as you value theirs.
You mentioned wanting to see your friends again, but it’s unclear if these two girls have moved away, or been apart from you for some reason. If they haven’t been around you lately, your constant thinking about them is natural, since you miss them! Do you have any way to be in touch with them over the summer?
You are still very young, and you might feel very frustrated with certain feelings at this age. However, time is on your side. You still have years of friendship ahead with Charlotte and Crystal, and years of time to get to know them more. In time, I'm sure they will open up to you or you to them about your feelings. Enjoy the summer and don't be hesitant to come back to Alterheros if you have more questions.