It's important to understand that 'jealousy' is a word applied to a variety of things, and can have different root causes. You have to determine what root cause is at work in your guys, to address it.
A.) Oftentimes it's caused by a person's preexisting insecurities, ranging from minor to severe. The stories we hear of really bad cases of jealousy (e.g. involving violence) fall under this. It's a sign that someone is at least a bit behind in their emotional development, and need self work. Sometimes we can help, but other times it's totally up to them to realize their problem and fix themselves.
B.) We can sometimes do things or behave in such a way that causes a person who is normally confident and secure to feel insecure. In that case, it's important that we right ourselves, step in to reinforce that person and the relationship. I shouldn't be inconsiderate of another person's needs to the point that it debases what would otherwise be a strong and happy relationship, then turn around and say "Well, you're just jealous!", when the reality is I have not given them nearly enough time or attention. I've seen "Well, you're just jealous" happen many times among poly relationships, which amounts to further inconsideration.
(there are probably other causes, but those two are the most common)
Based on the limited description you gave, I'm guessing the first guy falls into the (B) example, but I'm not so sure about the 30-minute texting guy. I think you might have spoiled him with so much attention that he feels entitled to it. Maybe some balance needs to be reached in how you spend your time between them? Maybe the second guy needs a reality check, and should be considerate of you and your other partners' time and feelings. If he continues getting upset when you don't immediately jump for him, maybe you should read aloud to him the definition of compersion.
