Upper leaves turning white-yellow from center
I have 6 giant Roma tomato plants, planted early June, now 6-7 feet tall with green fruit emerging. I applied a newspaper/straw mulch covering three weeks ago to stop a weed problem. Earlier this week, the upper leaflets of one branch of the largest tomato plant started turning white then yellow from the center (stem) near the yougnest leaves. The discoloration then extended to the edge of the leaf before the leaves die.
this has afflicted the top of only one shoot of the tomato plant. I clipped it off and noticed some aphids and small red bugs under the leaves.
So here's my question. Is this likely to be some incurable Curly Top virus, aphid damage or just nitrogen dificiency due to the new newspaper mulch just starting to break down. HELP! I don't want to lose my best plant(s).