I don't have as much information about BF as some others but my understanding is that (based on more recent studies) the iron in your breast milk is readily absorbed by LO. This means that although the iron stores which are there from birth are depleting, baby will still gain iron from your milk.
There some are guidelines for babies to have vitamin supplements, for example in the UK the guidance is for babies to have a vitamin drop each day (this is just a few liquid drops and easily given even if LO is not taking solids), off the top of my head I think it's vitamins A, C and D but this is the UK. Guides in your own country may be different.
WRT starting solids, a lot can happen in just a few weeks. Mine only sat up at 5.5 months, he did not put all sorts of things in his mouth which is supposed to be a sign for solids readiness, he had no interest in putting toys in his mouth, however he had been screaming at me since 4.5 months that he wanted my food. I held off for that month because he was not sitting and I had it in mind I wanted to wait until the advised 6 months. In the end I gave solids at 5.5 months which he put straight to his mouth proving that not all babies put toys in their mouth but do know what food is!
There is research showing that solids introduction should not be too late so whilst I wouldn't actively hold off (for long) from introducing solids neither would I be worried if your baby is not yet ready. In the early stages of introducing solids babies generally take very little anyway.
If you choose the purée route this would be just a teaspoon or two of purée once per day.
If you choose the BLW (baby led weaning) route you can offer a finger sized piece of your own meal for baby to self feed, he may just hold it, smell it, lick it, suck and gum it, or he may may eat it. This sort of introduction is not about getting him to eat lots, but to let him begin to learn about alternate sources of nutrition, to learn of the tastes and textures of different foods which your family eat.
I've known babies who show very little interest in food until more like 9 months but the offer, little tastes and learning is still taking place to some degree each day so that at 9 months when they got an appetite for solids it was no a totally new experience for them, rather it was a move towards taking larger portions of what they were already being offered.
If it was me, I would wait another couple of weeks and see where you are at then.