I see yellowing between the veins on the NEW top leaves while veins stay green, is it iron or manganese?

Interveinal yellowing on the youngest top leaves with green veins points most likely to iron deficiency, also called iron chlorosis. Iron is immobile in the plant, so the shortage shows on the new growth first, not the old leaves. The way to separate iron from manganese: iron chlorosis usually gives a fine, sharp green vein network on a clearly yellow leaf and appears on the very newest leaves, and it is very common on high pH alkaline or calcareous soils, in waterlogged spots, and on light sandy soils. Manganese deficiency also shows interveinal yellowing on young leaves but the contrast is usually less sharp, the veins look like a broader green band, and in some crops you get small dead spots or a mottled, grey speckled look. Honestly the two are hard to tell apart by eye, so a tissue test or soil test is the reliable answer. Please confirm before treating, and rule out waterlogging or root problems, which mimic both. For iron, a foliar spray of ferrous sulphate, often something like a 0.5 to 1 percent solution sprayed two or three times at weekly intervals on new growth, is the usual quick correction. For manganese, a foliar spray of manganese sulphate at a similar low concentration is used. Soil drenching with iron is often wasted on high pH soils. Always adjust the concentration and number of sprays to your crop and local KVK advice, and do not over-apply, because too strong a spray scorches leaves.