Hum...that looks like it as well...(!) I think I'll try rest the water for 48 hours before watering, see if it solves the problem. If not, I'll try to call some garden centers to see if they have something to eradicate the fusarium infection. Keeping my fingers crossed! Thank you :-)

I certainly hope it works out well. It is so unpleasant to deal with a bug. I feel bad for you. I learned a long time ago, a sick plant really bums me out, so If I give it all my effort and lose a plant, I just might deserve a new one. Sort of helps the sting as plant people get attached. Let us know how it goes for you.

I'm not familiar with fluoride toxicity, but the link says the brown stripes affect the white stripes on the leaves, but it looks like your problem is at the edges, including entirely green areas, of the leaves. It shouldn't be hard to get the results of water tests done by your local water authority; ours even posts them online. This will also tell you how hard your water is. Is the lava rock a top dressing or is it part of the mix? Is the mix fine and peaty? Are the damaged leaves limited to one branch or to the top or the bottom of the dracaena? The size of the plant would affect how often you water; a plant that large in that sized pot will dry that amount of soil pretty fast so you'll have to water more often. On the other hand, the amount of water you give it each time mainly depends on the type and amount of soil in the pot. Make sure that the bottom of the pot isn't sitting in drained water, which will allow minerals flushed from the soil to reenter the pot and keep the lower part of the pot saturated with water, which is deadly to roots. As you probably know, dracaenas love lots of light. I've seen them thrive directly under bright office fluorescents, especially if the lights are on all or most of the day. You're dracaena's corner looks very dark, though, so I'd move it directly under a set of lights to keep it in good condition. I hope something in there is helpful.

no plant holds all its leaves forever ... the oldest are the lowest ... and as the plant grows up ... you usually have to harvest a few down low ... hard to tell with this pic.. but it looks like one of the lowest ... just cut it off with scissors near the stem ... and be done with that leaf ... another plant that is getting large.. for the pot its in ... if you repot the other.. maybe this one can also be up-potted ... and.. once again.. there is a houseplant forum ... welcome to the forums .... ken