Good job... just a few adjustments.
Beelzebub 7 - Make sure everything is centered. "Weak", "Let's Explain" is a little high up. Next, make sure that if you have text covering a background, put a white border around it, "If baby Be'el isn't touching...". All text boxes need to end with punctuation, so "Don't cry..." and "it's ok, it's ok..." should have periods. And "He doesn't seem..." can just be white over the black background. You can use a light grey there or white since it is over a black background.
Beelzebub 11 - Make sure everything is centered. "oi oi" and "a punk from town..." are all left justified. And "Geeze" is too high up in the word bubble. "Trash" is too high up (but doesn't need punctuation since it is a single word statement), and "I'll start" needs punctuation.
Defense Devil 1 - Watch your fonts. "Master, work is work..." should be cc Zoinks and much larger. Same for "Judgement 2: Apple Tree 4".
For the rest, it's all the same. Punctuation, centering text in word bubbles, making sure the text is not too big in word bubbles.
Here is an example of cover text:
http://www.onemanga.com/Fairy_Tail/162/01/